Lasers are good pointers. Teachers use them in the classroom, pet owners use them to rev up their cats, and other civilizations may use them to draw attention to themselves. And someday, it might be possible for us to do the same thing.
A student-led research team at the University of California-Santa Barbara has been looking for laser signals from M31, the Andromeda Galaxy. It’s high in the west at nightfall right now. Under dark skies, it’s visible as a small, hazy patch of light.
The California students have been using a network of telescopes to photograph M31 at different times. It’s a small enough target that they can take in the whole thing — hundreds of billions of stars and perhaps a trillion planets.
They’re looking for changes — for a bright light that flickers on and off. Such a light could be a signal from an advanced civilization — a beacon designed to announce its presence to the universe. Since M31 is two and a half million light-years away, though, that civilization could have vanished long before a signal could reach Earth.
Another study, by a student at MIT, found that we could send our own signals — just not to another galaxy. But using high-power lasers beamed through giant telescopes, we could let nearby star systems know that we’re here. And with the right equipment, we could reach out as far as 20,000 light-years or more — through a good bit of our own galaxy.